OBJECTIVETo investigate the protective effect of urokinase on renal interstitial inflammation and fibrosis in rats with chronic cyclosporine A (CsA)-induced nephropathy.

METHODSMale SD rats were fed on low salt diet (0.05% sodium) for 7 days and randomized into 4 groups for treatment with CsA, CsA+continuous low-dose uPA (U2), intermittent CsA+ high-dose uPA (U6) or vehicle (control group). In the former 3 groups, the rats were subjected to daily intragastric administration of CsA (25 mg/kg) for 4 weeks to establish CsA-induced chronic nephropathy model, and those in U2 and U6 groups were given uPA at 2000 U/kg daily or at 6000 U/kg every 3 days, respectively. Four weeks after the treatment, the renal function and 24-h proteinuria were assessed, and Masson staining was used for examining fibrin deposition. Semi-quantitative immunohistochemical staining was employed for evaluation of ED-1-positive cells, urokinase-type plasminogen activator (uPA) and transforming growth factor-beta1 (TGF-beta 1).

RESULTSFour weeks after the treatment, the CsA-treated rats showed significantly elevated serum creatinine (Scr), blood urea nitrogen (BUN) and increased urine proteins. Continuous administration of low-dose uPA resulted in significantly reduced Scr, BUN and 24-h urine protein excretion, while intermittent high-dose uPA treatment did not produce such changes. CsA increased fibrin deposition, total number of macrophages in renal interstitium and TGF-beta1 expression in the renal tissue, which were significantly reduced in U2 group (P<0.05) but not in U6 group (P>0.05).

CONCLUSIONContinuous administration of low-dose uPA may reduce interstitial fibrin deposition and alleviate renal interstitial inflammation in rats with chronic CsA nephropathy, possibly by reducing the number of macrophages and TGF-beta1 expression in the renal tissue.